1. Field of the Invention
The present invention relates to a manufacturing method of micro-electro-mechanical systems device, and more particularly, to a manufacturing method capable of improving the stiction failure and the hermeticity failure of the micro-electro-mechanical systems device simultaneously.
2. Description of the Prior Art
With the advances of the technology, the industry keeps downsizing the consumer electronics while improving the quality and the functionality of the consumer electronics simultaneously. To meet the design concepts of the products, sensing devices (e.g. the sensor for sensing pressure, sound wave or acceleration) of the consumer electronics are usually realized by Micro-Electro-Mechanical Systems (MEMS) devices. The failure scenarios which frequently occur in MEMS devices include the stiction failure and the hermeticity failure.
In general, to prevent the stiction failure in the MEMS device, the prior art coats a monolayer on the MEMS structure of the MEMS device to prevent stiction between MEMS structures; for example, China Patent No.1314086C, U.S. Pat. No. 6,906,845, No. 7,045,170 and No. 20060246631 respectively provide a manufacturing method of coating the monolayer to improve the MEMS structure and prevent the stiction failure. Correspondingly, to prevent the hermeticity failure occurred in the MEMS device, the prior art implements a clean process to the bonding rings of the MEMS device and the cap wafer before bonding the MEMS device and the cap wafer. Therefore, the following bonding process benefits from the clean process, such that the water vapour and the dust are kept away from entering the MEMS device to further maintain the reliability of the MEMS device. However, the processes for preventing the stiction failure and the hermeticity failure in the prior art affect interactively, such that the stiction failure and the hermeticity failure may not be improved simultaneously.
For example, please refer to FIG. 1, which illustrates a process of a conventional manufacturing method of a MEMS device. As shown in FIG. 1, the MEMS structure of the MEMS device may be composed of a structure wafer and a cap wafer. Before implementing a eutectic bonding process to bond the cap wafer and the structure wafer, the clean process may be implemented to the cap wafer and the structure wafer to clean the bonding rings of the cap wafer and the structure wafer to avoid the hermeticity failure of the MEMS device. However, the clean process damages the monolayer which is coated during an anti-stiction coating process, such that the stiction failure may occur to the manufactured MEMS device.
Please refer to FIG. 2, which illustrates a process of a conventional manufacturing method of a MEMS device. Compared to the manufacturing method shown in FIG. 1, if the clean process is implemented before the surface modification process, the monolayer may be protected without damaged by the clean process, such that the stiction failure of the MEMS device may be avoided. However, before implementing the anti-stiction coating process to coat the monolayer on the structure wafer, the surface modification process is implemented to the structure wafer to modify the surface materials of the MEMS structure, such that the monolayer is easier to be coated on the surfaces of the MEMS structure. Under such a circumstance, the surface modification process degrades the bonding ring, such that the hermeticity failure is more likely to occur after the structure wafer and the cap wafer are bonded.
According to the above description, the processes for preventing the stiction failure and the hermeticity failure in the prior art affect interactively, such that at least one of the stiction failure and the hermeticity failure is more likely to occur in the MEMS structure. Therefore, how to improve the stiction failure and the hermeticity failure of the MEMS structure has become a primary objective in the field.